There are well-known valve timing control apparatuses for displacing the phase of relative rotation between a drive-side rotating member that rotates in time with a crankshaft and a driven-side rotating member that rotates in time with a camshaft in an automobile engine or other internal combustion engine, whereby valve timing can be appropriately adjusted and an appropriate operational state can be achieved. As an example of this type of valve timing control apparatus for an internal combustion engine, a configuration such as the following is disclosed in Patent Document 1.
As shown in FIG. 14, this valve timing control apparatus comprises an inner rotor 101 fixed to the distal end of a camshaft of an internal combustion engine; an externally mounted outer rotor 102 capable of rotating relative to the inner rotor 101 within a prescribed range; a phase-controlling mechanism that variably controls the phase of relative rotation between the inner rotor 101 and the outer rotor 102 and that includes a fluid-pressure chamber, which is formed between the inner rotor 101 and the outer rotor 102 and is divided into an advance chamber and a retard chamber by vanes assembled on the inner rotor 101; and a locking mechanism 103 for restricting displacement of the phase of relative rotation of the inner rotor 101 and the outer rotor 102.
The locking mechanism 103 is configured having a locking member 105 accommodated in a sliding groove 104 provided to the outer rotor 102; an urging spring 106 for urging the locking member 105 inward in the radial direction; and a concave engagement part 107, which is formed on the inner rotor 101, and into which the radially inward end (the distal end) of the locking member 105 is inserted when the phase of relative rotation between the inner rotor 101 and the outer rotor 102 is the maximum retard phase. The locking member 105 has a corner part 105a having an angular shape on the radially inward side and a corner part 105b having an arc shape on the radially outward side.
If hydraulic oil is supplied into the concave engagement part 107 of the locking mechanism 103 in a state in which the radially inward end of the locking member 105 is inserted into the concave engagement part 107, the locking member 105 moves outward in the radial direction and unlocks. Since the corner part 105b on the radially outward side of the locking member 105 is arc-shaped, sliding resistance due to tilting of the locking member 105 at this time can be alleviated, and friction on the sliding regions is reduced.
[Patent Document 1] Japanese Laid-open Patent Application No. 2003-013713 (p. 2-4, FIG. 2, FIG. 5)